Wiring question

Stranded wiring terminations using set-screws should be tinned or sleeved with a thin brass tube so that the compression of the set screw makes the connection tight both physically and electrically.

For two to four watt circuits used on AC electric clocks, just about the most important factor is making the connection physically strong.

Another consideration is "conductor gap." Any bare conductor should be separated from an opposite conductor or grounded metal or any metal likely to be grounded by an appreciable distance.

Lightning storms and power-line fault conditions can produce very high voltages on distribution wiring. Arc-over failures are common when sufficient conductor gap is not observed.

The opinion is mine alone and based on many years of observing power line faults and disturbances that have produced failures at the user interface.

Be safe and understand what you are doing.

 

Don't ever use tinned ends on screw connections. The solder creeps out and leaves connection looser in one to few years.

That how I know because I did this first long ago and caught this and redid with bare wires or as above suggest using crimped tube on bare wire.

Cheers, Watchfixer

 

Agree with the tinned wire and creep. Depending on the gauge of wire, I have had good success with just tight twist of the bare wires inserting and screwing down. ON fine gauge I will strip twice the amount of insulation and then twist tight, bend the bare wire back to double it, twist, insert and screw down.

 

I can agree to Watchfixer's comment about "solder creep" used to tin stranded electrical wiring. It is a common problem with screw connector blocks etc when the load is heavier than the connector's designed capacity.

However, my reply to larryn's query was very specific in which he asked about re-using a "power connector junction block, used between the 110 volt input and the field coil. It uses 4 set screws."

I believe his connector block is similar to that commonly used in older equipment in which a wire is inserted into the block laterally. A set-screw secures the connection both mechanically and electrically in this type connector as shown in the snapshot below.

Stranded wire will separate under compression unless individual strands are bonded with solder or crimped in a tube.

 

larry n wrote in part about tinned connections: "heavier amperage wiring circuits as found in cars, they do not tin/solder the wires as normal heat can soften the medium used."

That's true and over the years, the automobile manufacturing/repair industry has adopted crimp or swedged connectors. The swedge process is satisfactory until an over-current condition heats the junction or any resistive location in the conductor. Solder is still used within the storage battery and in the electronic components of automobiles

 

With connectors like these, and small gauge wires, I always double over the wire, and sometimes triple it over, to give a better chance for a good connection. Problems occur when a heavy gauge of wire is put into the same connector as the small wires. Then I usually make a twist connection before putting it into the connector, to ensure the smaller wire is fully connected..

 

Larry was the original wire twisted copper?. With this low power application it will be ok to twist, insert and screw down.

 

Like many responders to this question I have never been happy inserting twisted wire into connector blocks such as these. In my case I have adopted have adopted the following practice.
I find a piece of sold copper wire that fits into the connector block reasonably snugly- usually I find it in some of my spare house wiring cables- or worst case buy some from a hardware store or Radio shack. I then solder a piece of the stripped (no insulation) solid wire onto the parent (clock coil or AC wire ) - (all you need to do here is twist the stranded wire around the solid wire a few turns and then solder them together). Once soldered I slide a piece of heat shrink tubing over the resulting joint and shrink it onto the joint (make sure you use a size of tubing that provides a very tight fit when shrunk). This should leave you with a short piece of solid wire sticking out of the joint. All that is left to do is to trim the end of the solid piece of wire close to the joint so that no bare wire is exposed when you slide the solid wire end into the connector block. This makes for a neat looking connection that has little possibility of coming loose or shorting due to exposed strands of wire.

 

What I've often done is to quickly tin just the end of the
wire so that it doesn't fray but still screws down on the stranded
part. Some times I do have to trim a little of the soldered end because
it is difficult to control how much gets tinned.
I should also note that if your working with old exposed wire
you may find it hard to tin and solder.
Tinker Dwight

 

Tinning of wire ends was by code many years ago, but are no more or less banned. (Its banned here in Norway) Twisting is not a good solution (but may work when done with great accuracy), crimping on a ferrule will be the best. For a clock using a small current the issue of loose single copper threads making a risk for arc or short will be the main issue.

Fuses of as low value as practical, and gfci or even afci increases the safety are important to help to reduce the risk of fire, or electrocuting.

I understand it has been several threads about rewiring, grounding, reduced voltage etc. I feel that's good! These old clocks, you and your house are to important to take to many risks. This article made me look at things I didn't look for before. http://sound.westhost.com/clocks/ocm.html

dsk

 

Yes, Ill tell what I did:
Since I have a 230V supply with 2 live conductors I did put in a fuse in conductor no 2 (intended to be neutral).
Then I luckily got the idea to look at the old fuse, and someone had put in a 3.15Amp instead of 0.1Amp! That might be about as putting in a 472 Amp fuse to your std 15 Amp outlet, or actually no fuse at all.

So I just ask myselves, why did I not do that before? Do I never learn? etc. (no answer)

dsk

 

I've worked on thousands of clocks with telechron motors over the last 40+ years, and have yet to see a field coil short out. But, for safety, I agree that an in line fuse of low amp value should be added to the circuit, and old insulation checked. I have seen the insulation on the lead wires fail on telechron field coils, which is where the greatest danger is. Where possible, a grounded three wire plug should be used.

 

You are suppose to put the fuse on the hot wire, not
the neutral.
Tinker Dwight

 

You can see that this is a controversial topic - like the one on whether to connect wires to lugs by soldering or by crimp connectors, which will get about 50 posts whenever it is raised. Personally, when there is a terminal block with screws that compress the wire by pressing straight down, I have always just twisted the wire carefully.

I have more trouble with the old-fashioned plugs and similar connections where you must bend the wire around the shaft of the screw. What do people do there? In the very old days there were special screws called "binding head" designed for this purpose, but even so, it is hard to do perfectly with stranded wire. What do you do there?

 

Agree, but I have no neutral, almost like your 240/208 delta-vound supply. Both lines becomes live, with approx 130V to ground. Then both wires should have a fuse.
(This system was abandoned as a system in new areas they use aother systems.)

dsk

 

I would say (regardless of codes) you do it the right way. If possible I crimp on a ferrule or shoe, sometimes twisting and soldering.

dsk

 

On issues such as this subject it is best to follow the local and national codes. In the US the Electrical Code is NFPA 75. (National Fire Protection Association) The code is written and maintained by the manufacturer's association and the insurance underwriters laboratory or UL. Every country has its own code. In Germany its TUV.

Making repairs or modifications to an appliance that could cause harm puts the repairer at liability for loss. This is especially true when the repair or modification is performed as a paid-service or in conjunction with a service agreement.

I would suggest that all electrical repairs should be deferred to a qualified (licensed) electrician if the clock or item is being repaired. If, on the other hand, the repair is made on your own clock or electrical item, then you should think about who is going to pay to put out the fire.

 

A fuse on the Hot leg may offer some protection if Hot shorts to Neutral. However I feel the greatest risk with these old clocks is electrocution risk which could occur if Hot comes loose and touches a metal part like the coil frame, metal case, movement and ultimately the time setting knobs.

In the case of Telechron coils, the terminals/leads are held to the core of the coil with paper!! This paper turns brittle with time/heat and these connections become very weak mechanically. Any stress from the line cord can break the connections away from the core of the coil and can then float around inside the case of the clock. If Hot happens to touch metal and the owner sets the clock he'll likely get shocked.

There's nothing wrong with fusing a clock but IMHO the single biggest safety improvement is as follows:
1. Proper strain relief/wire management on any wiring inside the clock. (cord and coil wiring)
2. Wrap the coil with 3M #27 Glass Cloth Tape to reinforce that brittle/deteriorated paper covering
3. Use a 3 wire cord and attach ground to one of the screws holding the coil to the movement.
4. Use a GFI circuit.